Metal working oils such as forging oil, pressing oil, drawing oil, rolling oil, cutting oil, grinding oil and others comprise mineral oil, synthetic oil and/or hydrous oil (e.g., emulsion, solution, etc.), to which are added various oiliness agents and extreme-pressure agents as additives for the purpose of improving their working performance. Above all, the additives for forging oil are required to have load carrying capacity.
In internal-combustion engines, driving systems (automatic transmissions, buffers, power steering wheels, etc.), gears and others, used is lubricating oil for promoting their smooth operation. However, in the recent high-power and high-load situation for them, their lubricity is often unsatisfactory, thereby resulting in that the lubricative surface in them is exposed to much friction and worn whereby they may seize up. To evade the problem, therefore, various oiliness agents and extreme-pressure agents are added as additives to the lubricating oil for them. The additives are required to have good load carrying capacity. For meeting the requirement, various types of additives have heretofore been developed, but are still not fully satisfactory.
Recently, however, it has been said that some additives will have negative influences on the working environment and even on the natural environment. Therefore, it is desirable that the additives with that possibility are not used as much as possible. In particular, it is specifically said that additives containing chlorine or lead have negative influences on human bodies and the natural environment. In addition, it is said that zinc, molybdenum, alkali metals and alkaline earth metals will have the possibility of negative influences on the natural environment and the working environment.
The invention has been made in consideration of the matters noted above, and its object is to provide a novel additive composition having good load carrying capacity, in particular, to provide a novel additive composition having high load carrying capacity and having little possibility of negative influences on the working environment and the natural environment.